Temperature gauge needle position

2005 BMW X5 3.0i

Regrettably I never paid attention to the temperature needle position. I just got coolant flush and got the sensor and thermostat replaced. It’s frigid here in Chicago and the temperature needle was half way between blue and red when I was driving. Is this normal, too cold, too hot?

Once the car is warmed up, the temperature needle stays at the halfway point, or about 180F or so. If it is right between red (bad) and blue (bad, but not so bad), that should be the right position. Many car companies have dropped the temperature numbers since most car owners have no idea what they should be. The “red is bad” and “blue is cold” has some meaning.

If the gauge stays on blue it usually means that your thermostat is stuck open.

Doc explained it perfectly.

The needle is sitting exactly where it should be. Between the blue and the red zone.

The thermostat in your vehicle is rated at 206 degrees. That’s the temperature at which the thermostat opens. This is well above 180 degrees.

Once the thermostat opens, it’s up to the cooling system to keep the coolant temperature under control.

It’s winter time now. So if the thermostat opens at 206 degrees the coolant is probably running at 210-215 degrees.

When summertime comes, and the temperatures get hotter and you start using the air conditioning you’ll see the needle move up a little more. This is because of the higher ambient temperatures and because the condenser in front of the radiator is releasing heat. So the coolant temperature could get a high as 220-230 degrees depending on the conditions.

As long as the temperature gauge needle stays out of the red zone, the cooling system is operating properly.


+1 for Tester. I agree that the needle is right where it should be.

It’s probably fine but it’s possible for the gauge to read normal with an overheating engine if the resistance in the temp sender or sender connector has increased due to age. Increased resistance will drive the gauge needle down lower than what the actual temp is.
Same principle with a fuel gauge.

I’m in full agreement with Tester; just throwing some trivia out… :slight_smile:

I expect it is ok. It’s a good idea with a new car to mark the nominal warmed-up position with a sharpie on the dashboard so you can tell if it is deviating from that. Suggest you do it now. If you know somebody who has a 2005, no harm to look where their gauge resides.

On my Corolla the temp gauge is about 40% of full scale and steady when driving on the freeway. When in stop and go traffic it goes to 50% of full scale, at which point the radiator fan kicks on. I didn’t follow my own advice above and as a result had some difficult to diagnose symptoms b/c the coolant was too cold. Replacing the thermostat and the radiator fan temp switch eventually fixed it. I’ve since marked both those points on my dashboard temp gage.